1. Field of the Invention
The present invention generally relates to magnetic resonance imaging.
2. Description of Background
Magnetic resonance imaging (MRI) uses magnetic fields to image a tissue of a patient placed inside a powerful uniform magnetic field of an MRI scanner. The MRI scanner can align the magnetic moments of protons in the tissue (typically hydrogen protons of water molecules in the tissue) in the direction of the field, precessing about the field at their Larmor frequency. An excitation field (typically orthogonal to the main magnetic field) near the Larmor frequency is applied to alter the alignment of the protons in the tissue, typically flipping the magnetic moment of the protons in the main field. When the excitation field is turned off, the protons emit a photon that can be detected and processed to form an MRI image of the tissue.